"SALT Trial" Study of Ascending Levels of Tolvaptan in Hyponatremia

Inclusion Criteria * Hyponatremia in euvolemic or hypervolemic states, defined as serum sodium \<135 mEq/L prior to randomization * Able to give Informed Consent. Exclusion Criteria * Women who are breast feeding and females of childbearing potential who are not using acceptable contraceptive methods * Hyponatremia in hypovolemic states * Acute and transient hyponatremia associated with head trauma or post-operative state * Hyponatremia due to uncontrolled hypothyroidism or uncontrolled adrenal insufficiency * Cardiac surgery within 30 days of potential study enrollment, excluding percutaneous coronary interventions * History of a myocardial infarction within 30 days of potential study enrollment * History of sustained ventricular tachycardia or ventricular fibrillation within 30 days, unless in the presence of an automatic implantable cardioverter defibrillator * Severe angina including angina at rest or at slight exertion and/or unstable angina * History of a cerebrovascular accident within the last 30 days * Subjects with psychogenic polydipsia may not be included, however subjects with other psychiatric illness may be included * Systolic arterial blood pressure \< 90 mmHg * History of hypersensitivity and/or idiosyncratic reaction to benzazepine or benzazepine derivatives (such as benazepril) * History of drug or medication abuse within the past year,or current alcohol abuse * Uncontrolled diabetes mellitus defined as fasting glucose \> 300 mg/dL * Urinary tract obstru…